Hmm. By the 1960s, Stoeger was in South Hackensack, NJ, NOT New York, as is engraved on the rib. My earliest 1959 Stoeger catalog shows they were in New York, and lists the "Upland King", so, you may be a little bit off on the date. The catalog lists that gun as a single trigger gun, but, says custom options were available.
I think somebody did you a favor if they specified double triggers.
A fellow on my squad often brought a Zephyr Uplander, the less engraved version, to the club on league night, and there were never any malfunctions that I recall. His was a double trigger gun as well. Nice enough gun, I always thought.
Enjoy.


Best,
Ted